•Physico-chemical parameters of water column control Hg speciation in sediments.•Sediments from the middle of the estuary were contaminated by Hg.•Concentrations of Hg were less during the monsoon ...and post monsoon period.•Salinity, pH of water column may change Hg speciation of the bottom sediments.•TOC in sediments control Hg partitioning in the system.
Distribution and speciation of mercury (Hg) in the sediments from a tropical estuary (Godavari estuary) was influenced by the changing physico-chemical parameters of the overlying water column. The sediments from the upstream and downstream of the estuary were uncontaminated but the sediments from the middle of the estuary were contaminated by Hg. The concentrations of Hg became considerably less during the monsoon and post monsoon period. Total Hg concentrations and its speciation (at the middle of the estuary) were dependent on the salinity of the overlying water column. However, salinity had little or no effect on Hg association with organic phases in the sediments at downstream. Increasing pH of the overlying water column corresponded with an increase in the total Hg content in the sediments. Total organic carbon in the sediments played an important role in controlling Hg partitioning in the system. Uncomplexed Hg binding ligands were available in the sediments.
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•A benzothiazolinic spiropyran was synthesized with subsitutent at a unique position to bind metal ions.•The structure of the spiropyran derivative was established through x-ray ...crystallography.•The spiropyran derivative selectively detected highly toxic Hg2+ ions in aqueous solution.•The selectivity of the receptor was established using naked eye, digital imaging and spectroscopic techniques.•Computational studies established the stabilities of different stereoisomers of the receptor and their complex.
A substituted benzothiazolinic spiropyran was synthesized through a reaction between 2-hydroxy-3-methoxy-5-nitrobenzaldehyde and 2-ethyl-3-methylbenzodthiazol-3-ium-4-toluenesulfonate in the presence of piperidine. The spiropyran derivative was characterized using IR, NMR, mass and SCXRD analysis. Owing to the presence of a methoxy group ortho to the phenolic oxygen atom, the affinity of the synthesized spiropyran derivative towards toxic metal ions was investigated in CH3CN: water (1:1). A hypsochromic shift in the absorption and fluorescence spectra was observed in response to the presence of Hg2+ ions. The formation of complex was also observed through a visible change in color from dark yellow to colorless. UV–vis, fluorescence spectroscopy and digital image analysis were used to obtain good limit of detection value (5.5 μM, 78.5 nM and 0.62 μM, respectively) for the receptor towards Hg2+ ions. The 1H-NMR spectroscopy indicated the interaction of the phenolic oxygen atom and Hg2+ ions. The density functional theory was further used to investigate the stabilities of the different stereoisomers of the spiropyran derivative and their complex. The DFT studies also supported the interaction between the phenolic oxygen atom and the Hg2+ ions. TD-DFT studies were also performed to analyze the observed changes in the UV-Visible spectra upon addition of the Hg2+ ions, which indicates an increase in the HOMO-LUMO gap.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Mesoporous Ag3VO4/C3N4 heterojunction photocatalysts was performed via a sol–gel.•The Hg(II) reduction was completely achieved within 60 min through illumination.•2.4%Ag3VO4/C3N4 ...photocatalyst indicated much better photoreduction performance.•It was 4.3 and 5.4 fold larger Hg(II) reduction than that Ag3VO4 NPs and g-C3N4.•Mesoporous Ag3VO4/C3N4 showed high stability and recyclability for five times runs.
A facile and highly efficient mesoporous Ag3VO4/C3N4 heterojunction photocatalysts were synthesized by accommodating Ag3VO4 nanoparticles (NPs) onto the porous g-C3N4 nanosheets. The findings showed that mesoporous Ag3VO4 NPs uniformly disseminated onto the g-C3N4 with a small particle size (5 nm). Compared to pristine g-C3N4 and Ag3VO4 NPs, the mesoporous Ag3VO4/C3N4 photocatalysts displayed much higher photocatalytic Hg(II) reduction. It was found that among all the synthesized nanocomposites, the synthetic mesoporous 2.4%Ag3VO4/C3N4 photocatalyst indicated much better photoreduction performance. The Hg(II) reduction was completely achieved within 60 min (100%) through illumination by visible light, which was 4.3 and 5.4 fold larger photocatalytic performance than that Ag3VO4 NPs and g-C3N4, in that order. The enhancement Hg(II) reduction performance of mesoporous Ag3VO4/C3N4 photocatalysts could be explained by a synergetic effect of S-scheme heterojunction structure with high surface area and promotion light harvest, suggesting to efficacious of the photoinduced charges separation. The recycling performance of the nanocomposites exhibited superior stability, durability and reusability. S-scheme charge transfer route accomplished of mesoporous Ag3VO4/C3N4 with improved stronger redox ability and separation of photoinduced carriers. This research work clarifies an outstanding approach to promote a novel and facile S-scheme photocatalytic system to oxidize environmental contaminants and reduce toxic heavy metals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Assimilation of mercury (Hg) by vegetation represents one of the largest global environmental Hg mass fluxes. We estimate Hg assimilation by vegetation globally via a bottom-up scaling approach using ...tissue Hg concentrations synthesized from a comprehensive database multiplied by respective annual biomass production (NPP). As global annual NPP is close to annual vegetation die-off, Hg mass associated with global NPP approximates the transfer of Hg from plants to soils, which represents an estimate of vegetation-mediated atmospheric deposition. Annual vegetation assimilation of Hg from combined atmospheric and soil uptake is estimated at 3062 ± 607 Mg yr–1, which is composed of 2491 ± 551 Mg yr–1 from aboveground tissue uptake and 571 ± 253 Mg yr–1 from root uptake. Assimilation of atmospheric Hg amounts to 2422 ± 483 Mg yr–1 when considering aboveground tissues only. Atmospheric assimilation increases to 2705 ± 504 Mg yr–1 when considering that root Hg may be partially derived from prior foliar uptake and transported internally to roots. Estimated atmospheric Hg assimilation by vegetation is 54–137% larger than the current model and litterfall estimates, largely because of the inclusion of lichens, mosses, and woody tissues in deposition and all global biomes. Belowground, about 50% of root Hg was taken up from soils with currently unknown ecological and biogeochemical consequences.
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The threat connected to mercury results from its capacity to be transported over long distances and its ability to bioaccumulate and biomagnify in the trophic chain, making it a global problem. ...Humans are situated at the top of the trophic ladder, and excess mercury manifests itself mainly in the onset of neurological conditions. The toxicity of mercury, as well as its residence time, depends on the form in which it occurs. However, analysis of mercury speciation is time-consuming and poses a high risk of additional or negative contamination. Hence, the mercury thermodesorption method, and particularly its use for fractionating Hg, offers many new possibilities. Here, the thermodesorption technique was applied to the determination of mercury fraction in particulate matter using a DMA-80 direct mercury analyser (Milestone, Italy). The presented method allows direct (without prior mineralisation) determination of labile and stabile mercury fractions within a relatively short time. Heating sample in subsequent temperatures enables determination the share of mercury adsorbed on the surface (mainly associated with halogenides (Hgads1) and HgSO4/HgO/HgF2 (Hgads2), as well as absorbed within the suspended particulate organic matter (Hgabs), in a relatively short time. This fractionation is of great importance in terms of estimating the transfer of mercury to and along the trophic chain. This method determines the contribution of two stable mercury fractions:: HgS and residual Hg, strongly bound to particulate matter matrix (Hgres). The novelty of this technique is also its joint ability to determine gaseous mercury bound to airboirne particulate matter, which will enable better understand Hg cycling in the atmosphere as well as mercury fraction in dry deposition flux. This method enables assessment of global mercury circulation in environment.
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•Method enables recognition of Hg adsorbed and absorbed on/in the organic matter.•Innovative method of analysing gaseous Hg adsorbed on particulate matter in air.•Method may verify residual time and transport of Hg in the atmosphere.•Presented method may be implemented by many laboratories.
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The sea surface microlayer (SML) is the uppermost ∼1000 μm of the surface of the ocean. With distinct physicochemical properties and position relative to the adjacent subsurface waters (SSWs), the ...ubiquitous distribution and high dynamics of the SML greatly regulate the global air–sea gas exchange and biogeochemistry. Mercury (Hg) redox chemistry in surface seawaters and air–sea exchange of gaseous Hg (mainly Hg(0)) fundamentally control the global oceanic Hg cycle. However, the occurrence and transformation of Hg in the SML have been poorly quantified. Here we optimize the traditional SML sampling system to make it more suitable for dissolved gaseous Hg (DGM, mainly Hg(0)) sampling. We then assess the temporal and spatial variability of DGM, total Hg, dissolved organic carbon (DOC), and Hg redox chemistry in the SML and SSWs of diverse marine environments. Our data suggest a general DGM, total Hg, and DOC enrichment in the SML relative to the SSWs but with complex variability in time and space. The incubation experiments further reveal the complex characteristics of Hg redox chemistry between the SML and SSWs. We discuss important implications of the SML Hg cycle on air–sea Hg exchange and suggest wider investigations of the SML Hg cycle in the global hydrosphere.
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•Accumulation of Hg in sediments is influenced by finer particles (silt and clay).•The increasing complexation/reduction processes of Hg by DOM decrease Hg sequestration.•TOC and DOM control ...sequestration of Hg by sediments.
Total organic carbon (TOC) (in sediment) and dissolved organic matter (DOM) (in water column) play important roles in controlling the mercury sequestration process by the sediments from the central east coast of India. This toxic metal prefers to associate with finer size particles (silt and clay) of sediments. Increasing concentrations of DOM in overlying water column may increase complexation/reduction processes of Hg2+ within the water column and decrease the process of Hg sequestration by sediments. However, high concentrations of DOM in water column may increase Hg sequestration process by sediments.
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Mercury (Hg) is a volatile, bioaccumulative, and toxic heavy metal, and its global distribution is controlled by the Hg biogeochemical cycle in the atmosphere-land-ocean systems and the deep Hg cycle ...in interior reservoirs (e.g., mantle and crust). The biogeochemical cycle has been relatively well studied, but the deep Hg cycle remains relatively poorly constrained. Mercury isotopes undergo mass-dependent fractionation (MDF) and unique mass-independent fractionation (MIF) which can provide good constraints on large-scale Hg cycling. In this review, we provide a summary of available results on Hg abundance and isotopic composition in the atmosphere-land-ocean systems and interior reservoirs, with a focus on linking the Hg biogeochemical cycle to the deep Hg cycle. Through this effort, a few key points can be pointed out: (1) Natural and anthropogenic activities release large amounts of Hg into the atmosphere, which is transported on a global scale and deposited in terrestrial and marine systems; (2) Major constituents of the mantle and crust, e.g., mid-ocean ridge basalts (MORBs) and granites, show much lower Hg abundance than the atmosphere-land-ocean systems due to volcanic Hg(0) degassing and the formation of Hg-bearing ore deposits; (3) Mercury isotopes, especially Δ199Hg values, are useful in tracing surface Hg recycling into mantle and crust; (4) Hg(II) photo-reduction in the atmosphere yields negative Δ199Hg values in gaseous Hg(0) and positive Δ199Hg values in Hg(II) species, which results in negative Δ199Hg values in terrestrial systems (dominant deposition of Hg(0)) and positive Δ199Hg values in marine systems (dominant deposition of Hg(II); (5) MORBs and arc-related basalts (IABs) show positive Δ199Hg values, suggesting marine Hg recycling into the oceanic crust and upper mantle via plate subduction. Oceanic island basalts (OIBs) and continental flood basalts (CFBs) mostly display near-zero Δ199Hg values, suggesting limited surface Hg recycling into the lower mantle. Granites show positive to negative Δ199Hg values, suggesting the continental crust receives Hg from the metasomatized mantle and remelted terrestrial material. Opposing Δ199Hg values in arc-related and intracontinental hydrothermal systems highlights the great potential of using Hg isotopes for metallogenic tracing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reducing Hg contamination in soil using eco-friendly approaches has attracted increasing attention in recent years. In this study, a novel multi-metal-resistant Hg-volatilizing fungus belonging to ...Lecythophora sp., DC-F1, was isolated from multi-metal-polluted mining-area soil, and its performance in reducing Hg bioavailability in soil when used in combination with biochar was investigated. The isolate displayed a minimum inhibitory concentration of 84.5mg·L−1 for Hg(II) and volatilized >86% of Hg(II) from LB liquid medium with an initial concentration of 7.0mg·L−1 within 16h. Hg(II) contents in soils and grown lettuce shoots decreased by 13.3–26.1% and 49.5–67.7%, respectively, with DC-F1 and/or biochar addition compared with a control over 56days of incubation. Moreover, treatment with both bioagents achieved the lowest Hg content in lettuce shoots. Hg presence and DC-F1 addition significantly decreased the number of fungal ITS gene copies in soils. High-throughput sequencing showed that the soil fungal community compositions were more largely influenced by DC-F1 addition than by biochar addition, with the proportion of Mortierella increasing and those of Penicillium and Thielavia decreasing with DC-F1 addition. Developing the coupling of Lecythophora sp. DC-F1 with biochar into a feasible approach for the recovery of Hg-contaminated soils is promising.
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•A novel metal-resistant Hg(II)-volatilizing fungus, Lecythophora sp. DC-F1, was isolated.•DC-F1 and biochar both effectively reduced Hg(II) contents in soil and plants.•The soil with both bioagents exhibited the lowest Hg uptake in lettuce shoots.•Soil fungal abundance and community structure were influenced to a greater degree by DC-F1 addition than by biochar addition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Identifying Hg sources to aquatic ecosystems and processes controlling the levels of monomethylmercury (MMHg) is critical for developing efficient policies of Hg emissions reduction. Here we measured ...Hg concentrations and stable isotopes in sediment, seston, and fishes from the various basins of the Baltic Sea, a large brackish ecosystem presenting extensive gradients in salinity, redox conditions, dissolved organic matter (DOM) composition, and biological activities. We found that Hg mass dependent fractionation (Hg-MDF) values in sediments mostly reflect a mixing between light terrestrial Hg and heavier industrial sources, whereas odd Hg isotope mass independent fractionation (odd Hg-MIF) reveals atmospheric inputs. Seston presents intermediate Hg-MDF and odd Hg-MIF values falling between sediments and fish, but in northern basins, high even Hg-MIF values suggest the preferential accumulation of wet-deposited Hg. Odd Hg-MIF values in fish indicate an overall low extent of MMHg photodegradation due to limited sunlight exposure and penetration but also reveal large spatial differences. The photodegradation extent is lowest in the central basin with recurrent algal blooms due to their shading effect and is highest in the northern, least saline basin with high concentrations of terrestrial DOM. As increased loads of terrestrial DOM are expected in many coastal areas due to global changes, its impact on MMHg photodegradation needs to be better understood and accounted for when predicting future MMHg concentrations in aquatic ecosystems.
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